Into the midst of the cloud, the God that called him enabling him to enter and abide there; whereas, when he was left to himself, he could not enter into the tabernacle, Exodus 40:35. Forty days and forty nights; in which he did neither eat nor drink, Exodus 34:28 Deuteronomy 9:9,18; whereby it seems most probable the six days mentioned Exodus 24:16 were a part of these forty days, because Moses being in perpetual expectation of God's call, seems not to have had leisure for eating and drinking, nor provision neither. Besides, he is not said to be in the midst of the cloud so long, but only in the mount, where he was those six days, Exodus 24:15,16.
Related Commentaries of Exodus 24:18
Exodus 24:18
18 And Moses went into the midst of the cloud, and gat him up into the mount: and Moses was in the mount forty days and forty nights.